As said in the past, if you can show how far you've got, you're more likely to get assistance.

I have previously worked for a number of retail companies both as a technical support analyst and developer of in-store systems so have a lot of experience with EPoS systems. The one we used at my last employer was infact written in VB6 with a mix of C++ components and VB scripts.

Personally, I think you'd find it much easier to write one for what you need than trying to understand an existing EPoS system before fudging your own around the base of another.

As said in the past, if you can show how far you've got, you're more likely to get assistance.

I have previously worked for a number of retail companies both as a technical support analyst and developer of in-store systems so have a lot of experience with EPoS systems. The one we used at my last employer was infact written in VB6 with a mix of C++ components and VB scripts.

Personally, I think you'd find it much easier to write one for what you need than trying to understand an existing EPoS system before fudging your own around the base of another.